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Nowhere to Hide II (Posted on 2005-01-26) Difficulty: 2 of 5
What is the least number of white knights that can be placed on a standard chessboard so that a black piece cannot be added to an unoccupied square without being under attack?

See The Solution Submitted by Juggler    
Rating: 4.0000 (1 votes)

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Solution Complete Solution | Comment 7 of 11 |

In my previous post, I demonstrated an example with 12 knights.

To see that 12 is optimal, note that no knight can cover (either occupy or attack) more than one square labeled x in the following diagram:

x x . . . . . x
. x . . . . x x
. . . . . . . .

. . . . . . . .

. . . . . . . .

. . . . . . . .
x x . . . . x .
x . . . . . x x

Thus, at least 12 knights are required, which proves that the answer is 12. 


  Posted by David Shin on 2005-01-27 07:50:03
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